Ample evidence now indicates that the metabolism of triglyceride-rich lipoproteins is closely related to that of high density lipoproteins. In a series of three studies, these relationships will be explored in normolipidemic individuals whose high density lipoprotein-cholesterol concentrations vary widely in order to determine: 1) the extent to which ambient HDL-cholesterol levels affect triglyceride transport; 2) the effects of altered rates of enteric or hepatogenous triglyceride transport upon the composition of HDL and the formation and transport of HDL cholesteryl esters as related to ambient HDL levels. Both short-term effects of different fat-rich meals and sustained effects of diets enriched in saturated fats, polyunsaturated fats, carbohydrates and ethanol will be evaluated. Methods to be applied to the analysis of triglyceride-rich lipoproteins and species of HDL separated by ultracentrifugation and by polyacrylamide gel electrophoresis include: lipid analysis; radioimmunochemical analysis of apoproteins, including apo A-I, apo A-II, apo D and apo E; measurements of size distribution by laser light-scattering and electron microscopy; analysis of ordered structure in HDL-core lipids by circular dichroism; and measurements of rate of esterification of cholesterol in plasma. The results of this research are expected to illuminate functional relationships between plasma triglyceride transport in humans and the formation and metabolism of HDL. The data obtained may also be useful in the design of diets that minimize atherosclerotic risk.